1. Field of the Invention
The present invention relates to a substrate processing apparatus for forming a predetermined pattern (for micro devices, e.g. a semiconductor device, a liquid crystal device, a CCD, a thin-film magnetic head, a magneto-optic disc, etc.) on a thin substrate, e.g. a semiconductor wafer, a liquid crystal substrate, etc., by successively subjecting the substrate to patters forming processes, i.e. coating of a photosensitive material (photoresist), mask pattern exposure, and development.
2. Related Background Art
To produce a semiconductor device by lithography processes, a substrate processing system is used which consists essentially of a coater for coating a photoresist on a semiconductor wafer (hereinafter referred to simply as xe2x80x9cwaferxe2x80x9d), an aligner (exposure apparatus), e.g. a stepper, for exposing the photoresist to light according to the image of a pattern of a reticle (or a photomask or the like), and a developer for developing the photoresist on the wafer, as disclosed, for example, in U.S. Pat. No. 4,900,939.
It has recently been demanded to produce micro devices, particularly semiconductor devices, at a higher throughput (the number of products produced per unit time). Accordingly, there is a need to shorten the time required to transfer a wafer from a coater to an aligner and the time required to transfer a wafer from an aligner to a developer and to control the cycle time (the difference in processing time between the processing systems). Therefore, the conventional substrate processing apparatus has a wafer stocker disposed near or inside the aligner and further has a wafer loader system for delivering the wafer between the stocker and the aligner (or exposure system).
In the above-described conventional apparatus, wafers transferred from the coater are temporarily stored into the stocker through the wafer loader system, and when preparation for exposure has been completed, the wafers in the stocker are successively loaded into the aligner (or exposure system) through the wafer loader system. Upon completion of exposure, each wafer is delivered to the developer by using the wafer loader system again. The wafer loader system is composed of a plurality of transfer shafts which are arranged to intersect each other, and arms which move along these transfer shafts.
Wafers are generally formed with a cut portion (orientation flat, notch, etc.) for positioning with respect to the angle of rotation. In the aligner, the cut portion of a wafer must align with a predetermined direction. However, the rotation angle of a wafer delivered from the coater to the aligner is not fixed. Therefore, the conventional substrate processing apparatus is provided with a pre-alignment device for setting the wafer loaded into the aligner so that the cut portion of the wafer aligns with a predetermined direction.
Thus, the conventional substrate processing apparatus uses a special-purpose wafer loader system to load and unload wafers into and from the aligner, and further uses a special-purpose pre-alignment device to effect rough positioning of wafers. Accordingly, the time required to transfer a wafer from the coater to the aligner and the time required to transfer a wafer from the aligner to the developer cannot be made shorter than a predetermined time for the reasons stated below, and there therefore limits improvement of the throughput in the production of semiconductor devices:
{circle around (1)} Since wafer loading and unloading operations are carried out by using arms on the same transfer shaft, the wafer loading and unloading positions in the aligner are the same. Consequently, the path for loading and the path for unloading overlap each other, resulting in each wafer passing along the useless overlap path. For this reason, the transfer time is lengthened.
{circle around (2)} The wafer loader system has a plurality of transfer shafts, and every time a wafer shifts from one transfer shaft to another, the delivery of the wafer is carried out between arms. Accordingly, each individual wafer must be delivered an unfavorably large number of times throughout the apparatus.
{circle around (3)} Since a special-purpose pre-alignment device is used, the time for pre-alignment is added to the actual exposure time.
{circle around (4)} In the conventional substrate processing apparatus, the aligner is provided with a special-purpose wafer loader system and a special-purpose pre-alignment device. Therefore, the overall size of the aligner becomes large, thus making it difficult to construct the substrate processing apparatus in a compact form.
An object of the present invention is to provide a compact substrate processing apparatus which is designed so that the number of transfer shafts is reduced, and the time required to exchange wafers is reduced, and further a pre-alignment device provided in an aligner (exposure system) is simplified, or the need for such a pre-alignment device is eliminated, thereby enabling an improvement of the throughput in production of micro devices such as semiconductor devices.
Another object of the present invention is to provide a substrate processing apparatus which is designed so that loading of a substrate from a photosensitive material coating system into an exposure system and unloading of the substrate from the exposure system to a developing system can be carried out at the same side of the exposure system.
The present invention provides a substrate processing apparatus which has: a photosensitive material coating system (5) in which a photosensitive material is coated on a substrate (10) as an object of processing; an exposure system (21) which has a substrate stage (25 and 26) for positioning the substrate coated with the photosensitive material in the photosensitive material coating system, and in which the substrate is exposed to light according to the image of a mask pattern; and a developing system (36) in which development is carried out on the substrate that has been subjected to mask pattern exposure in the exposure system. The substrate processing apparatus includes: a pre-alignment device (17) for setting the rotation angle of the substrate, which has been coated with the photosensitive material in the photosensitive material coating system, to a predetermined angle; a first substrate transfer system (11 and 12) for transferring the substrate to the exposure system while maintaining the rotation angle set by the pre-alignment device; and a second substrate transfer system (37 and 38) for transferring the substrate to the developing system from a position in the exposure system which is different from a position to which the substrate is transferred from the photosensitive material coating system.
The substrate processing apparatus may be arranged such that the photosensitive material coating system (5E) and the developing system (36E) are disposed in parallel so that loading of the substrate from the photosensitive material coating system (5E) to the exposure system (21E) and unloading of the substrate from the exposure system (21E) to the developing system (36E) are carried out at the same side of the exposure system (21E).
According to the present invention, the photosensitive material coating system (5), the exposure system (21) and the developing system (36) are disposed in a row, so that the substrate coated with a photo sensitive material is loaded onto the substrate stage (25 and 26) in the exposure system (21) through the first substrate transfer system (11 and 12), and upon completion of exposure, the substrate stage (25 and 26) is moved to set the substrate to an unload position. Then, the substrate is transferred to the developing system (36) from the unload position through the second substrate transfer system (37 and 38). That is, the substrate stage (25 and 26) is also used as a part of the substrate transfer system, thereby reducing the number of transfer shafts, and thus shortening the substrate exchange time (delivery time).
Further, since the first substrate transfer system (11 and 12) transfers the substrate while maintaining the rotation angle set by the pre-alignment device (17), no pre-alignment device is needed in the exposure system (21). Accordingly, it is possible to reduce the overall installation area (foot print) of the exposure system (21), in which high-performance air conditioning is required.
If the photosensitive material coating system (3E) and the developing system (36E) are disposed in parallel to each other so tha t loading of the substrate from the photosensitive material coating system (5E) to the exposure system (21E) and unloading of the substrate from the exposure system (21E) to the developing system (36E) are carried out at the same side of the exposure system (21E), the substrate is transferred along a U-shaped path, including the path of transfer by the substrate stage (25 and 26).
Thus, in the present invention, loading of the substrate into the exposure system and unloading of the substrate from the exposure system are respectively carried out by the first substrate transfer system, which is provided in the photosensitive material coating system, and the second substrate transfer system, which is provided in the developing system, and the substrate stage, which is provided in the exposure system, is used as one of transfer shafts. Accordingly, the number of special-purpose transfer shafts required in the whole apparatus decreases, and the number of deliveries required for each substrate (wafer or the like) decreases, resulting in a reduction in the time required to transfer the substrate. Therefore, there is an improvement in the throughput of the process in which a substrate is coated with a photosensitive material and then subjected to exposure and development. At the same time, the overall size of the substrate processing apparatus can be reduced. In addition, since the number of deliveries required for each substrate can be reduced, generation of dust can be suppressed, and thus an improvement in reliability can be expected.
Further, since pre-alignment of the substrate is carried out in the photosensitive material coating system, no pre-alignment is needed in the exposure system, and it is only necessary to carry out exposure in the exposure system. Accordingly, the throughput further improves. In addition, since it is possible to minimize the area required for installation of the exposure system, in which high-performance air conditioning and vibration isolation are required, it is also possible to minimize the reinforcement required for the building construction such as enhancement of the floor strength and vibration isolation structure, which are particularly needed in the exposure system.
In layout at a factory, for example, if a plurality of substrate processing apparatuses are arranged in parallel by disposing a photosensitive material coating system, an exposure system and a developing system in a row for each substrate processing apparatus, processing systems in which the same processing is carried out, e.g., the photosensitive material coating systems, can be arranged on the same line. Thus, it is possible to simplify the piping for chemicals and pneumatic equipment, the wiring for signal cables, and the piping for air conditioning carried out for temperature and humidity control and dust removing.
When the exposure system in the substrate processing apparatus of the present invention is a step-and-scan projection aligner, the substrate stage is particularly suitable for use as one of transfer shafts because it serves to scan the substrate in a predetermined direction. Accordingly, the substrate transfer time can be further shortened.
Further, when the photosensitive material coating system and the developing system are disposed in parallel so that loading of the substrate from the photosensitive material coating system into the exposure system and unloading of the substrate from the exposure system to the developing system are carried out at the same side of the exposure system, the substrate processing apparatus, including the photosensitive material coating system, the exposure system and the developing system, can be arranged in a compact form.